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Documents reveal new details about the Boston Marathon bombings and aftermath

Prosecutors argue that information Tsarnaev gave to FBI should be admissible

Tsarnaev's attorneys ask judge to throw out evidence, arguing it was coerced

The Boston Marathon bombing suspects used Christmas lights and model-car parts to make the explosives, prosecutors said in court documents obtained by CNN on Wednesday.

"The Marathon bombs were constructed using improvised fuses made from Christmas lights and improvised, remote-control detonators fashioned from model car parts," federal prosecutors said in a motion filed Wednesday. "These relatively sophisticated devices would have been difficult for the Tsarnaevs to fabricate successfully without training or assistance from others."

To obtain explosive fuel for the pressure cookerbombs, the filing says, brothers Dzhokhar and Tamerlan Tsarnaev "appeared to have crushed and emptied hundreds of individual fireworks containing black powder."

Suspects tied to Boston bombings – Dias Kadyrbayev, left, with Boston Marathon bombing suspect Dzhokhar Tsamaev in a picture taken from the social media site VK.com. Kadyrbayev is expected to plead guilty August 21 to charges in connection with removing a backpack and computer from Tsamaev's dorm room after the April 2013 bombing, according to a defense lawyer.

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Suspects tied to Boston bombings – Bombing suspect Tamerlan Tsarnaev was killed during the shootout with police in Watertown, Massachusetts, on April 19, 2013. He is pictured here at the 2010 New England Golden Gloves.

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Suspects tied to Boston bombings – Dzhokhar Tsarnaev was captured in a Boston suburb on April 19, 2013, after a manhunt that shut down the city. In July, he pleaded not guilty to killing four people and wounding more than 200.

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Suspects tied to Boston bombings – From left, Azamat Tazhayakov and Dias Kadyrbayev went with Boston bombing suspect Dzhokhar Tsarnaev to Times Square in this photo taken from the social media site VK.com. A federal grand jury charged Tazhayakov and Kadyrbayev with obstructing justice and conspiracy to obstruct justice relating to the removal of a backpack from Tsarnaev's dorm room after the bombings. Tazhayakov was convicted of conspiracy and obstruction charges in July 2014. He faces up to 25 years in prison at his sentencing in October. He has filed an appeal.

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Suspects tied to Boston bombings – Robel Phillipos, a U.S. citizen, was also arrested on May 1, 2013. He was charged with lying to federal agents about the bombing, according to court papers.

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Suspects tied to Boston bombings – Phillipos, Tazhayakov and Kadyrbayev are accused of removing items from Tsarnaev's dorm room after the bombings on April 15, 2013. The items they took included a backpack containing fireworks that had been "opened and emptied of powder," according to the affidavit.

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Suspects tied to Boston bombings – The FBI released photos and video on April 18, 2013, of two men identified as Suspect 1 and Suspect 2 in the deadly bombings at the Boston Marathon. They were later identified as Dzhokhar Tsarnaev, 19, and his brother Tamerlan Tsarnaev, 26.

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Suspects tied to Boston bombings – Boston Police released surveillance images of Dzhokhar Tsarnaev at a convenience store on April 19, 2013.

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Suspects tied to Boston bombings – The FBI tweeted this photo on April 19, 2013, and urged Watertown residents to stay indoors as they searched for the second suspect.

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Suspects tied to Boston bombings – The FBI released photos and video on April 18, 2013, of two men it called suspects in the deadly bombings and pleaded for public help in identifying them. The men were photographed walking together near the finish line.

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Suspects tied to Boston bombings – A man identified as Suspect 2 appeared in this photograph by bystander David Green, who took the photo after completing the Boston Marathon. Green submitted the photo to the FBI, he told Piers Morgan in an interview.

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Suspects tied to Boston bombings – The man identified as Suspect 2 appears in a tighter crop of David Green's photo.

It's not time yet for prosecutors to make their full case against Dzhokhar Tsarnaev, but as attorneys spar over what evidence can be used in the high-profile death penalty case against him, the description of what materials were used to make the bombs was among several new details about last year's terror attack and its aftermath included in court documents.

The motion also includes additional details about the note Dzhokhar Tsarnaev allegedly wrote while he was hiding out inside a boat in a backyard in Watertown, Massachusetts.

"God has a plan for each person," Tsarnaev wrote, according to the court document. "Mine was to hide in this boat and shed some light on our actions."

In their 29-page motion, prosecutors detail Tsarnaev's medical care while at Boston's Beth Israel Deaconess Medical Center, arguing that information from more than 11 hours of FBI interrogations while he was hospitalized should be admissible.

Prosecutors cite several reasons why they needed to question Tsarnaev without reading him his Miranda rights against self-incrimination and without allowing him access to a lawyer.

Evidence law enforcement had at the time, they argue, suggested a possible larger conspiracy. FBI agents had "reason to believe that the Tsarnaevs had accomplices and that they or others might have built additional bombs that posed a continuing danger to public safety."

The note scribbled inside the boat referred to others, saying, "we are promised victory and we shall surely get it," according to Wednesday's motion.

Also, a search of the Tsarnaevs' homes failed to uncover traces of the black firework powder used to build the pressure cooker bombs, suggesting that it had been built elsewhere and with help. The Christmas lights used as fuses and the model-car remote control used to detonate the devices also suggested a level of sophistication that suggested terrorist training, prosecutors said.

Tsarnaev was lucid while hospitalizedand was not coerced into making any of the statements, they argue.

According to the court documents, Tsarnaev was questioned about 22 hours after undergoing surgery for multiple gunshot wounds.

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He had been weaned off the sedative propofol but was still on pain medication. FBI agents questioned him on and off over a nearly 38-hour period, conducting 14 interviews and giving Tsarnaev frequent breaks, including a 10½-hour stretch so he could sleep, the court documents say.

Prosecutors say the FBI's interview took time because doctors had performed a tracheostomy to allow greater airflow. Tsarnaev initially answered by nodding or writing in a notebook and then later spoke his answers. Although Tsarnaev denied that anyone else was involved, authorities believed he might be lying or concealing the involvement of others, according to prosecutors.

Government officials have maintained that Tsarnaev was questioned under the "public safety" exception to the Miranda warnings, which allows for limited questioning of a suspect by law enforcement to determine whether there is imminent danger of an attack.

"The fact that Tsarnaev was in the hospital recovering from bullet wounds does not mean the interview was coercive or that the agents who conducted it did anything wrong," the prosecutors' motion says.

Tsarnaev, prosecutors allege, wanted to explain the bombings and take credit for them.

"As the note he wrote in Watertown on the inside of the boat reflects, Tsarnaev was eager to take credit for his crimes and 'shed some light' on their meaning. That indeed is a common practice among terrorists," the motion says.

They argue that the statements were involuntary, that the public safety exception agents used didn't apply to the interrogation and that Tsarnaev's first court appearance was postponed to allow for additional questioning.

FBI agents questioned Tsarnaev, his attorneys argue, "despite the fact that he quickly allayed concerns about any continuing threats to public safety, repeatedly requested a lawyer, and begged to rest as he recovered from emergency surgery and underwent continuing treatment for multiple and serious gunshot wounds."

They also argue that the FBI agents deliberately misled Tsarnaev about his brother's death.

Prosecutors say that FBI agents didn't tell Tsarnaev about his brother's death "or the manner of that death, to spare him emotional trauma."

CNN first learned of the new court documents from multiple local media reportson Twitter.